1. Field of the Invention
The present invention relates to a treatment solution supply apparatus for supplying a treatment solution to a substrate such as a glass substrate, a semiconductor wafer or the like.
2. Description of the Related Art
TMAH (tetra methyl ammonium hydroxide) which is an undiluted developing solution of a positive type resist for a semiconductor is in increasing demand year by year as an undiluted solution for a semiconductor photo resist and a developing solution for TFT liquid crystal, while the collection and recycling of TMAH solution waste are becoming a problem. In the case of recycling, since the dispense condition becomes unstable due to clogging of a filter or the like caused by foreign matters contained in the recycling TMAH, it is required to stably control the dispense amount. As the art controlling the dispense amount, there are known a method of controlling a revolution frequency of a pump and a method of using a pump of constant pressure type.
FIG. 4 is a graph showing a first transition characteristic of a pump motor in a conventional treatment solution supply apparatus, wherein the relationship between an instantaneous flow amount (L/second) and time (second) in the case where the servo revolution frequency is fixed by the manual operation and the motor is started only by the revolution frequency control of the motor is shown. When starting the motor, the instantaneous flow amount reaches 7 L/second in a second and 9 L/second in two seconds so as to exceed the preset revolution frequency. Further, in three seconds it is overshot up to 12 L/second or more and although it is inclined to decrease from 4 seconds later, there is 8.5 L/second of the instantaneous flow amount still in five seconds and it takes 9 seconds to allow the instantaneous follow amount to stabilize at 8 L/second.
In Patent document 1, as shown in FIG. 5, there is disclosed an operation control method of a quantitative pump for transporting a predetermined amount of liquid waste from a flow control tank to a treatment tank in a liquid waste treatment facility. Namely, there is disclosed such art that an inverter for controlling the revolution speed of a pump and an electromagnetic flow meter for measuring the discharge amount are used together, a signal from the electromagnetic flow meter is fed back to the inverter or an external control device to allow the inverter or the external control device to automatically control the revolution speed so as to fix the discharge amount at a predetermined level, and a cleaning operation is carried out by increasing the revolution speed just after starting the pump or just before stopping it or only for a predetermined fixed period just after the starting or just before the stopping.
Moreover, in Patent document 2, there is disclosed art of supplying substantially a fixed amount of a developing solution into a wafer surface in such a manner that an inside of a supply nozzle is divided in the longitudinal direction thereof to form a plurality of treatment solution channels, and a moving speed of the supply nozzle is changed in each of solution applying regions of a wafer to allow the discharge amount per unit area within a scanning distance to be fixed at the same level even if the discharge amount is varied by changing the pumping pressure of the pump in each of the solution applying regions.
Patent document 1: Japanese patent application publication No. 2005-9329
Patent document 2: Japanese patent application publication No. 2003-197516
In the art of Patent document 1, an inverter control is carried out and the operation frequency is controlled with an alternating current motor by an inverter method. In the case of operating a general purpose motor by an inverter, a frequency-torque characteristic has a peak as shown in FIG. 5. In this example the peak is 60 Hz and torque values decrease on both sides of the peak, especially on a low frequency (revolution frequency) region so that a starting torque is inclined to a shortage. Although as a method of improving the shortage of torque in the low revolution frequency region, there are a method of using an exclusive inverter motor and a method of using variable voltage and variable frequency control, there is a problem that each of the methods requires an increase in costs.
In the art of Patent document 2, it is possible to control the flow amount, but the pump pressure is low and a discharge amount per unit time of the developing solution is small so that it is required to decrease the moving speed of the nozzle and increase the time that the nozzle stays in the predetermined region in order to increase the solution applying period. Therefore, there is a problem that it takes time for ensuring the predetermined discharge amount of the developing solution.